What is especially notable about Cook’s announcement is how drastically the climate has changed for gay people in corporate America, even in the past 10 years.

The case of Lord John Browne, who began his tenure as CEO of BP in 1995, underscores just how fast attitudes have shifted.

For years, the executive hid his sexuality from his peers in favour of carrying with him a constant fear that someone, somewhere might have discovered he was gay.

And in 2007, he resigned from his CEO job three months earlier than planned in hopes of preventing a London tabloid from continuing to report on his relationship with Jeff Chevalier, a man he met through the escort agency Suited and Booted.

The early resignation cost Browne more than $US30 million in stock and retirement benefits, and he blames the decision on his years of leading a double life.

“If you want to hide your sexuality, it’s very difficult to find people in the open,” he explains to NPR’s Audie Cornish in an interview that aired this past June. “Therefore, you might go elsewhere and you begin to create a pretty dangerous situation.”

In it, he expresses regret at not coming out during his time at BP and encourages other prominent business leaders to do so. In fact, he told Businessweek in June that workers who disclose their sexuality make their companies more profitable by allowing themselves to focus on doing their work instead of maintaining a heterosexual image.

In a statement provided to Business Insider, Browne called Cook’s decision to make his sexuality public, “an important step in the journey towards full and uncompromising inclusion of LGBT people.”

“By deciding to speak publicly about his sexuality, Tim Cook has become a role model, and will speed up changes in the corporate world,” Browne says. “It is a significant moment for Tim, for Apple, and for LGBT people everywhere who continue to grapple with their own private struggles.”